As a process for preparing an aromatic carbonate ester by, for example, transesterification of an aliphatic carbonate ester with an aromatic hydroxy compound or aromatic carboxylate has been known. In particular, as a process for preparing diphenyl carbonate as a kind of aromatic carbonate esters, many methods have been proposed. For example, U.S. Pat. No. 4,533,504 discloses a process for preparing diphenyl carbonate by reacting dimethyl carbonate as a kind of aliphatic carbonate esters with phenyl acetate as a kind of aromatic carboxylates.
Moreover, Japanese Patent Publication (Tokukaihei) No. 3-291257 discloses a process for preparing a diphenyl carbonate as a target product using a continuous multistage distillation column (reactive distillation equipment) in which a reaction of dimethyl carbonate with phenol as a kind of aromatic hydroxy compounds is carried out to generate methyl phenyl carbonate, and then methyl phenyl carbonate is disproportionated to produce diphenyl carbonate.
In the method disclosed in U.S. Pat. No. 4,533,504, the conversion of dimethyl carbonate is as high as 70 mole percent or more. However, since this method is a batch system, high productivity cannot be achieved. Therefore, diphenyl carbonate can not be prepared efficiently by this method.
The method disclosed in Japanese Patent Publication (Tokukaihei) No. 3-291257 also suffers from low productivity because the conversion of dimethyl carbonate is around 1.6 mole percent to 24 mole percent. Additionally, in this method, since diphenyl carbonate is obtained by disproportionation of methyl phenyl carbonate, many processing steps need to be carried out to prepare the diphenyl carbonate. Thus, the diphenyl carbonate cannot be prepared efficiently by this method.
Therefore, there is a great demand for a process that ensures efficient preparation of diphenyl carbonate, i.e., aromatic carbonate ester. Namely, in order to solve the above-mentioned problems associated with the conventional methods, it is an object of the present invention to provide a process for continuously and efficiently preparing aromatic carbonate esters.